Thread controlling mechanism for sewing machines

ABSTRACT

Thread controlling devices for the needle thread and looper thread of a two thread chainstitch sewing machine in which a thread takeup element is arranged to move in a path closely adjacent to the opposed edges of a pair of thread frictioning plates to draw the thread at times lengthwise between the thread frictioning plates and at other times laterally therebetween.

United States Patent Inventor Ralph E. Johnson Boonton, NJ Appl. No. 864,349 Filed Oct. 7, 1969 Patented Feb. 9, 1971 Assignee The Singer Company New York, N.Y. a corporation of New Jersey THREAQMCONTROLLING MECHANISMS FOR SEWING MACHINES 9 Claims, 9 Drawing Figs.

u.s.c| 112/247 1111.01 00511 49/00 Field of Search 112/247,

References Cited UNITED STATES PATENTS 1,761,349 6/1930 Kozlowski 2,173,320 9/1939 DeVoe Primary Examiner-Patrick D. Lawson Assistant ExaminerGeorge H. Krizrnanich Attorneys-Marshall J. Breen, Chester A. Williams, Jr. and

Robert E. Smith ABSTRACT: Thread controlling devices for the needle thread and looper thread of a two thread chainstitch sewing machine in which a thread takeup element is arranged to move in a path closely adjacent to the opposed edges of a pair of thread frictioning plates to draw the thread at times lengthwise between the thread fricfioning plates and at other times laterally therebetween.

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INVENTOR. Ralph E. Johnson BY W al'bv ATTORNEY WITNESS! awe h. vwulk THREAD CONTROLLING MECHANISMS FOR SEWING MACHINES BACKGROUND OF THIS INVENTION In the formation of stitches by machine it is conventional to subject each of the threads which must be actively manipulated in the stitch fonning process to the action of a thread controlling system. Such thread controlling systems provide during the various phases of each stitch forming cycle, for example, such diverse functions as movement of quantities of thread to and from selected places in the system, for the application of tension to the thread at particular times during each cycle, and for providing reserve supplies of thread in case of abnormal demand. Where the utmost of control is to be applied to the sewing thread, prior art thread controlling systems have included (I a takeup device for paying out and drawing in the thread which the sewing instrumentalities manipulate, (2) a tension device, (3) devices for controlling the disposition and movement of thread in the thread controlling system such as thread snubbers, auxiliary takeups, etc., and (4) slack thread controllers such as check springs for providing a cushion against the possibility of sudden abnormal thread demands. It is conventional in the prior art for each of the above listed control functions to be provided by a separate device. The US. Pat. application Ser. No. 773,507, filed Nov. 5, 1968 cluding a takeup 16, a tension device 26, a thread snub 29 for keepirLloose thread above the needle eye durin iescent of SUMMARY OF THE INVENTION It is an object of this invention to provide a thread controlling system in which the thread is guided from a source of supply to a thread tensioning device, a movable takeup element, and then to the sewing instrumentality apparently providing for only the takeup and tensioning functions discussed above. Because of the nature and relationship of these elements, however, they perform the functions of control over thread disposition within the system and of check spring action in responding to sudden abnormal thread demands. This invention thus provides for the elimination of a number of separate devices usually required for nicety of thread control without any loss of function normally provided by the eliminated devices.

The objects and advantages of this invention are attained by the provision of a movable takeup element having a path of motion always contiguous to and more closely adjacent the edge of a pair of opposed thread frictioning plates than is the guide which directs thread between the frictioning plates. With this arrangement, the thread at stitch setting, when the amount of thread used in the previous stitch must be drawn through the frictioning plates, will extend in a substantially straight line between the takeup and the guide for directing the thread to the tension device so that the thread will be drawn lengthwise between the frictioning plates. At other times in a cycle of stitch formation, however, the takeup will move to positions laterally offset from the point wherein the thread traverses the frictioning plates. As a result, a loop of thread will be formed between the takeup and the thread frictioning plates. The size and shape of this loop of thread can be controlled precisely by varying such factors as the positional relationship of the parts and the pressure by which the frictioning plates are biased together. Since the resistance to movement of the thread laterally between the frictional plates is but a small fraction of that which is associated with movement of the thread lengthwise therebetween, the loop of thread formed by the interaction of the takeup and the tension providing a ready source of additional thread to meet any suddcn demand. The thread loop, since its size may be controlled, also serves as a regulator of the disposition of thread within the thread controlling system, i.e., it can hold back slack thread from entanglement with the point of a descending nee- QI the like.

DESCRIPTION OF THE DRAWINGS With the above and additional objects and advantages in view as will hereinafter appear, this invention comprises the devices, combinations, and arrangements of parts hereinafter described and illustrated in the accompanying drawings of a preferred embodiment in which:

FIG. I represents a head end elevational view of a sewing machine with this invention applied thereto with the needle illustrated in top dead center position and having the sewing head cover removed and portions of the frame illustrated in cross section;

FIG. 2 is a side elevational view of the head end portion of the sewing machine of FIG. I with the bed illustrated in cross section taken substantially along line 2-2 of FIG. 1;

FIG. 3 is an enlarged horizontal cross sectional view of the mechanism adjacent the stitching point in the bed taken slightly below the level of the work support substantially along line 3-3 of FIG. I and showing thread in the looper thread controlling system;

FIG. 3A is an enlarged side elevational view of a fragment of the sewing head of FIG. 2 showing the needle thread takeup and thread frictioning plates with thread in a position of the parts substantially corresponding to that of FIG. 3;

FIG. 4 is an enlarged perspective view of the looper, needle and looper thread frictioning plates with thread, shown in a position of needle penetration into the looper thread loop;

FIG. 4A is an elevational view of the needle thread takeup similar to that of FIG. 3A but in a position of parts substantially corresponding to that of FIG. 4;

FIG. 5 is an enlarged perspective view of the looper, needle, and looper thread frictioning plates with thread, shown in a position with the looper in an extreme loop shedding position;

FIG. 5A is an elevational view of the needle thread takeup similar to that of FIG. 3A but in a position of parts substantially corresponding to that of FIG. 5; and

FIG. 6 is an enlarged cross sectional view of the thread tensioning plates of the looper thread controlling system taken substantially along line 6-6 of FIG. 4.

Referring to FIGS. 1, 2, and 3, a sewing machine is illustrated of the type adapted to produce atwo-thread chain stitch seam (federal stitch type 401) to which this invention has been applied to provide the control for both of the threads forming the chainstitch seam. Indicated at 11 in the drawings is the work supporting bed of the sewing machine from which rises a standard 12 supporting a bracket arm 13 overhanging the bed and terminating in a sewing head 14 which may be closed by an end cover 15. An arm shaft 16 journaled in the bracket arm 13 and a looper drive shaft 17 journaled in the bed are operatively connected by actuating mechanism (not shown) to drive the stitch forming instrumentalities of the sewing machine in timed relation. A needle bar 18 endwise reciprocable in beating bushings l9 and 20 in the sewing head 14 is reciprocated by means of a counterbalanced crank 21 and a drive link (not shown) from the arm shaft 16. An eyepointed thread carrying needle 22 is secured to the needle bar 18 for endwise reciprocation therewith and a needle thread takeup arm 23 is secured as by a fastening screw 24 to a split clamp 25 which is secured to the needle bar 18. A thread en- 'gaging eyelet 26 in the free extremity of the needle thread takeup arm engages and manipulates the needle thread to device serves the function of a conventional check spring in partment 30 in bushings 31 and 32 therein for turning and endwise sliding movement is a loopcr supporting rock shaft 33 which is arranged substantially perpendicular to the axis of the looper drive shaft 17. The looper rock shaft 33 is fonned within the compartment with a flattened enlarged section 34 having a projection 35 at each side. The projections 35 em-.

brace a connecting link 36 which is Hfurcated to embrace the flat section 34 of the rock shaft and is pivoted on a pin 37 secured in the enlarged section 34 and laterally offset from the axis of the loopcr rock shaft 33. The connecting link 36 at the opposite extremity is formed with a spherical tip 38 which is embraced by a spherical split clamp 39 formed on a link 40 which is pivoted on a pin 41 extending between spaced flanges 42 formed on a crank 43 fixed on the loopcr shaft 17. As the shaft 17 rotates, the connecting link 36 will describe a conical path of motion which because of the pin 37 will impart an oscillation to the looper rock shaft 33. A pin projecting upwardly from the connecting link 36 is embraced by a slide block 51 which is s constrained in a slot 52 formed in the compartment 30 of the machine frame. The spaced relation of the pins 37 and 50 gives rise to an axial shift of the loopcr rock shaft 33 in the bushings 31 and 32 as the shaft 17 rotates. Secured to the looper rock shaft 33 outside the compartment 36 as by a clamp screw 53 is a loopcr carrier 54 having attached thereto a loopcr 55 which thus partakes of the oscillation of the rock shaft 33 to move in a loop seizing and a loop shedding motion and the endwise movement of the rock shaft 33 to partake of the needle avoiding movement. As shown in FIGS. 3, 4, and 5, the loopcr 55 is formed with a blade 56 having a thread eyelet 57 near the free extremity and a heel portion 58 having a thread accommodating bore 59 through which the loopcr thread is directed toward the thread eye 57. The compartment 30 in which the looper driving mechanism is accommodated may be closed at the bottom by a cover 60 which may include a gasket 61 providing an oiltight compartment for this mechanism so that the parts may be lubricated and kept free of lint and other abrasive foreign materials.

Also carried in the bed in bearings such as that illustrated at in FIG. 3 is a feed advance rock shaft 71 which may be operated by conventional connections (not shown) with the sewing machine actuating mechanism. A rock frame 72 secured to a feed bar 73 which carries a feed dog 74 which works upwardly through suitable slots in a throat plate 75 as illustrated in FIGS. 1 and 2. .loumaled in a bushing 76 in the bed 1 1 is a feed lift rock shaft 77 having a rock arm 78 secured thereto in which is fixed a pin 79 embraced by a bifurcated portion 80 of the feed bar to impart raising and falling movements to the feed dog. As shown in FIG. I the feed dog may be formed with an aperture 81 through which the looper 55 operates. Opposing the feed dog above the throat plate 75 is a presser foot 82 carried by a presser bar 83 joumaled in the sewing head 14 and spring biased downwardly in a conventional fashion.

The path of the needle thread is best illustrated in FIG. 2 and extends from a source of supply (not shown) to a thread guide on the sewing machine bracket arm 13. The thread then extends from the thread guide 90 to a tensioning device indicated generally at 91 then directly to the eyelet 26 of the needle thread takeup arm 23 and to a thread guide 92 on the needle bar to the eye of the needle 22.

The needle thread tension device 91 comprises a support block 93 formed with an elongate aperture 94 by which the block is secured adjustably on the sewing head 14 by means of a securing bolt 95. An abutment screw 96 threaded into the sewing head 14 may be used to assist in locating the support block 93 but the fastening bolt may serve along to secure the support block on the sewing head. A guide pin 97 projects from the support block at the lower extremity thereof, and a threaded stud 98 projects from the support block intermediate its ends. A pressure plate 99 is apertured to embrace the threaded stud 98 and formed with a notch 100 embracing the guide pin 97 so that the pressure plate is thus located on the support block 93. An adjusting nut 101 on the threaded stud 98 adjusts the pressure applied to the pressure plate 99 by a light spring 102 on the threaded stud 98. The thread which is directed from the guide 90 to the takeup eyelet 26 passes between the support block 93 and the pressure plate 99 above the threaded stud 98. It will be noted from FIG. 2 and from the path of the takeup arm which is indicated in dot and dashed line in FIG. 5A that thetakeup arm 23 is disposed closely adjacent to the support block 93 and pressure plate 99 while the eyelet 90 which guides the thread to the takeup device is spaced many times farther from the takeup device than the takeup arm 23. As a result, movement of the takeup arm 23 along the tension dev'ice causes the thread to be wiped laterally between the support block 93 and the pressure plate 99. When the takeup arm 23 is at the top of its stroke as illustrated in FIG. 2 and FIG. 3A, thread will be drawn through the tension device from the source of supply, and in being so drawn the thread will pass lengthwise between the support block 93 and the pressure plate 99. When being drawn lengthwise between the pressure producing surfaces a considerably greater resistance is applied to the thread than when the thread is moved laterally therebetween, and as a result, when the takeup arm 23 occupies any other than its uppermost position, the tension device will cause a bend or loop to form in the thread at the opposite side of the takeup arm 23 from the needle as shown in FIGS. 4A and 5A. This loop of thread serves to influence the disposition of the thread in the system, for instance, to prevent the thread from piling up in front of the descending point of the needle. The loop of thread which is formed between the tension device and the takeup arm, as shown in FIGS. 4A and 5A, serves the additional purpose of providing a ready source for additional length of thread in the event that an abnormal demang hg ld suddenly arise, and in this respect the takeup mechanism operates in the same fashion as does a coventional check spring in the usual thread manipulating system. The pressure plate 99 above the adjusting nut 101 may be formed with a shallow recess 103 which serves to reduce the mass of the free limb of the pressure plate above the adjusting nut. By reducing the mass of this portion of the part a quicker response to changes in thickness of the thread and the like will be experienced.

Referring to FIGS. 2, 4,5, and 6, the loopcr thread tensioning device indicated generally at 109 together with the looper thread manipulating mechanism will now be described.

Secured by a fastening screw 110 to the bed 11 is a block 111 having inclined upper extremity. As best shown in FIG. 6 a support block 112 having a substantially flat upper surface 113 is secured on the block 111 by a fastening screw 1l4 having an internally threaded bore 115. Disposed on the flat upper surface 1 13 of the support block 112 is a pressure plate 116 which is preferably formed with an internal elongate aperture 117. The pressure plate at one side of the aperture 117 is formed with a thread engaging rib 118 having the full thickness of the pressure plate so that the rib 118 is opposed to the flat upper surface 113 of the support block. At the other side of the aperture 117, rib 119 of the pressure plate 116 is recessed or cut away so as to provide a thread clearance opening over the upper surface of the flat upper surface 113 of the support block. A leaf spring 120 is disposed above the pressure plate 116 and is fonned with a notch 121 which embraces a pin 122 projecting upwardly from the support block 112 and through an aperture in t l 1e p ressure plate 116. Arr adjusting screw 123 which is threaded into the internally threaded bore 115 of the fastening screw 114 serves to apply a regulatable amount of pressure between the pressure plate 116 and the support block 112. Referring to FIG. 3, a thread guide directs the looper thread from a source of supply (not shown) to a thread guide 131 from which the thread is directed between the pressure plate 116 and the support block 112 of the thread tensioning device. The thread then passes directly to the bore 59 in the heel 58 of the looper taker 55 and then to the work. As shown in FIG. 5 of the drawings, the .heel 58 of the loop taker partakes of an oval path indicated in dotted and dashed lines, and the bore 59 is everywhere closer to the opposed thread tensioning surfaces provided between the thread engaging rib I18 and the flat upper surface 113 than is the thread guide 131 from which the thread is introduced to the tensioning device. As a result of this disposition of parts, the thread is drawn laterally between the pressure plate and the flat upper surface of the support block except when increments of thread are drawn into the tensioning device from the source of supply. The reduced resistance applied to the thread with respect to such lateral movement as compared with the endwise movement through the tensioning plates acts above described with the respect to the needle thread mechanism to form a loop of thread at the opposite side of the looper from the stitches being formed. In this way, the slack thread is positioned within the system advantageously away from the possibility of entanglement near the point of the looper and a ready supply of thread is available in the case of sudden demand. The position of parts is illustrated in FIG. 3 when the looper is at its extreme loop seizing position corresponding to the point in each stitch forming cycle in which looper thread is drawn through the tension device from the source of supply. The particular arrangement of the spring 120 as indicated in FIGS. 3, 4 and 5 applies the greatest force between the support block 112 and the pressure plate 116 at the point at which the thread is located when it is drawn through the tension device from supply. At other times in the stitching cycle the thread will be moved laterally between the frictioning plates into positions in which lesser degrees of pressure will be applied thereto. It is pointed out that this gradient of pressure existing between the thread frictioning surfaces of the tensioning element exists in both the needle thread controlling system as well as in the loop taker thread manipulating mechanism. In the loop taker thread manipulating mechanism the pressure is greatest at the point at which the thread is disposed when the thread is drawn from supply, while in the needle thread tensioning device the reverse is true and the tension is least at the point in which the needle thread is disposed when it is drawn through the tension device from the supply. The reason for this apparent contradiction is that in forming chainstitches the needle thread is drawn from supply at a different point in the stitch forming cycle than the setting of the stitch. Whereas the needle thread is drawn from supply in the position of parts illustrated in FIG. 2, the stitch is set insofar as the needle thread is concerned in the position of parts illustrated in FIG. 5A, that is, only after the previous needle thread loop has slipped from the loop taker. The looper thread on the other hand is the passive thread in the stitch forming sequence and is set into the seam simultaneously with the withdrawal of additional thread from supply in the position of parts illus-' t ted in FIG-i elements to shift thread engaged thereby lengthwise between said thread engaging surfaces of said thread tensioning elements during withdrawal of thread from said source of thread supply and to shift the thread laterally between said thread engaging surfaces of said thread tensioning elements at other times during each stitch forming cycle.

2. A device for controlling the thread extending on a sewing machine from a source of thread supply to stitches being formed comprising a pair of thread tensioning plates having complemental substantially planar thread engaging surfaces biased into opposition, a thread takeup element including a thread accommodating eyelet, means for moving said thread accommodating eyelet in a path substantially within the plane of the thread engaging surface of said thread tensioning plates and uniformly spaced from said thread tensioning plates, a stationary thread guide for directing thread to be controlled between the thread engaging surfaces of said thread tensioning plates a thread proceeding directly from said stationary thread guide to said thread engaging surfaces of said thread tensioning plates and proceeding directly from said thread engaging surfaces of said thread tensioning plates to said thread accommodating eyelet in said takeup element, said stationary thread guide being arranged substantially within the plane of the thread engaging surface of said thread tensioning plates and spaced from said thread tensioning plates a distance I greater than the distance between said thread engaging sur- The thread coifirolling mechanisms of this invention, there fore, may be applied to either the needle thread or the looper thread of a sewing machine and are susceptible to a wide range of adjustments to suit varying conditions which may be called for in the concatenation in the sewing threads. The proximity of a moving takeup element to the tensioning plate may be selected, the gradient of pressure between the thread tensioning plates may be selected .and adjusted, and the ratio of dimensions of the path of the moving thread takeup element relatively to the position of the thread guide which leads thread to the thread tensioning device may be selected, all of these factors provide for control of the specific manner in which the thread will be manipulated by the device.

I claim:

1. A device for controlling the thread extending on a sewing machine from a source of thread supply to stitches being formed comprising a pair of thread tensioning elements having complemental thread engaging surfaces biased into 0pp0sition, a stationary thread guide engaging a thread from said source of supply and directing said thread between said compieinental thread engaging surfaces of said thread tensioning elements, a thread engaging takeup. member constrained to move in a path everywhere closer than said stationary thread guide to said complemental thread engaging surfaces of said thread, tensioning elements, means for imparting movement to said thread takeup member relatively to said thread tensioning face of said thread tensioning plates and said path of the take- RPlhFQ9E9ELQQI H5YL 3. A device for cgntrolling thethread extending on a sewing machine from a source of thread supply to stitches being formed comprising a thread guide, a thread takeup eyelet, and a stitch forming instrumentality engaging said thread in seriatim between said thread supply and said stitches, means for moving said thread takeup eyelet in a path such that the locus of straight lines between said thread takeup eyelet and said thread guide describes a substantially triangular surface, a pair of thread tensioning plates formed with opposed thread engaging surfaces, means for biasing said thread tensioning plates into opposition, means for supporting said thread tensioning plates with said opposed thread engaging surfaces substantially coinciding with at least a portion of the surface described by said locus of straight lines between said takeup eyelet and said thread guide, and with the edges of the opposed engaging surfaces of said thread tensioning plates which face said thread takeup eyelet being disposed everywhere closer to the path of said takeup eyelet than to said thread guide.

4. A thread controlling device as set forth in claim 3 in which the edges of the opposed thread engaging surfaces of said thread tensioning plates which face said thread takeup eyelet are disposed substantially equidistant from the path of said takeup eyelet.

5. A thread controlling device as set forth in claim 3 in which said means for biasing said thread tensioning plates into opposition includes means for establishing a pressure gradient between said opposed thread engaging surfaces.

6. A thread controlling device as set forth in claim 5 in which the location on said opposed thread engaging surfaces at which the highest pressure is applied corresponds to the location between said thread engaging surfaces of the thread extending between said thread guide and said takeup eyelet at stitch setting.

7. A thread controlling device as set forth in claim 3 in which said means for moving said thread takeup eyelet simultaneously imparts movement in a like path to said stitch forming instrumentality.

8. A thread controlling device as set forth in claim 7 in which said thread takeup eyelet is carried by and moves with said stitch forming instrumentality.

9. A thread controlling device as set forth in claim 8 in which said stitch forming instrumentality comprises an eye pointed thread carrying looper foi' a two thread iaifiiifEi sewing machine and in which said thread takeup eyelet is car'- ried on the heel of said looper. 

1. A device for controlling the thread extending on a sewing machine from a source of thread supply to stitches being formed comprising a pair of thread tensioning elements having complemental thread engaging surfaces biased into opposition, a stationary thread guide engaging a thread from said source of supply and directing said thread between said complemental thread engaging surfaces of said thread tensioning elements, a thread engaging takeup member constrained to move in a path everywhere closer than said stationary thread guide to said complemental thread engaging surfaces of said thread tensioning elements, means for imparting movement to said thread takeup member relatively to said thread tensioning elements to shift thread engaged thereby lengthwise between said thread engaging surfaces of said thread tensioning elements during withdrawal of thread from said source of thread supply and to shift the thread laterally between said thread engaging surfaces of said thread tensioning elements at other times during each stitch forming cycle.
 2. A device for controlling the thread extending on a sewing machine from a source of thread supply to stitches being formed comprising a pair of thread tensioning plates having complemental substantially planar thread engaging surfaces biased into opposition, a thread takeup element including a thread accommodating eyelet, means for moving said thread accommodating eyelet in a path substantially within the plane of the thread engaging surface of said thread tensioning plates and uniformly spaced from said thread tensioning plates, a stationary thread guide for directing thread to be controlled between the thread engaging surfaces of said thread tensioning plates a thread proceeding directly from said stationary thread guide to said thread engaging surfaces of said thread tensioning plates and proceeding directly from said thread engaging surfaces of said thread tensioning plates to said thread accommodating eyelet in said takeup element, said stationary thread guide being arranged substantially within plane of the thread engaging surface of said thread tensioning plates and spaced from said thread tensioning plates a distance greater than the distance between said thread engaging surface of said thread tensioning plates and said path of the takeup thread accommodating eyelet.
 3. a device for controlling the thread extending on a sewing machine from a source of thread supply to stitches beinG formed comprising a thread guide, a thread takeup eyelet, and a stitch forming instrumentality engaging said thread in seriatim between said thread supply and said stitches, means for moving said thread takeup eyelet in a path such that the locus of straight lines between said thread takeup eyelet and said thread guide describes a substantially triangular surface, a pair of thread tensioning plates formed with opposed thread engaging surfaces, means for biasing said thread tensioning plates into opposition, means for supporting said thread tensioning plates with said opposed thread engaging surfaces substantially coinciding with at least a portion of the surface described by said locus of straight lines between said takeup eyelet and said thread guide, and with the edges of the opposed engaging surfaces of said thread tensioning plates which face said thread takeup eyelet being disposed everywhere closer to the path of said takeup eyelet than to said thread guide.
 4. A thread controlling device as set forth in claim 3 in which the edges of the opposed thread engaging surfaces of said thread tensioning plates which face said thread takeup eyelet are disposed substantially equidistant from the path of said takeup eyelet.
 5. A thread controlling device as set forth in claim 3 in which said means for biasing said thread tensioning plates into opposition includes means for establishing a pressure gradient between said opposed thread engaging surfaces.
 6. A thread controlling device as set forth in claim 5 in which the location on said opposed thread engaging surfaces at which the highest pressure is applied corresponds to the location between said thread engaging surfaces of the thread extending between said thread guide and said takeup eyelet at stitch setting.
 7. A thread controlling device as set forth in claim 3 in which said means for moving said thread takeup eyelet simultaneously imparts movement in a like path to said stitch forming instrumentality.
 8. A thread controlling device as set forth in claim 7 in which said thread takeup eyelet is carried by and moves with said stitch forming instrumentality.
 9. A thread controlling device as set forth in claim 8 in which said stitch forming instrumentality comprises an eye pointed thread carrying looper for a two thread chainstitch sewing machine and in which said thread takeup eyelet is carried on the heel of said looper. 